Response Process of The Winter Soil Moisture of Different Vegetation Types to Rainfall Events in Karst Slope Land

: Understanding the response process of the soil moisture of different 10 vegetation types to rainfall in karst regions in winter is of great significance to the 11 implementation of various ecological restoration projects. However, at present, the 12 related research is mainly focused on nonwinter seasons, so there is less winter 13 research. Therefore, in this study, in Guanling County, Anshun City, southwestern 14 Guizhou Province, four types of vegetation, grassland, arable land, shrubland, and 15 forestland, were selected as sample plots, and the degree 、 time and speed responses of 16 the soil moisture of the vegetation types to rainfall were calculated using the time 17 series data of the soil moisture of different vegetation types. The results showed that 18 among the four kinds of vegetation in karst regions in winter, the response degree of 19 the grassland soil moisture to rainfall was largest, response duration was longest, and 20 response speed was fastest. Also, the increment of the soil moisture in the adjacent arable land soil layers significantly changed. In addition, in light rain events, only the 22 soil moisture of the grassland and arable land responded. Overall, in this study, 23 quantitative indices were used to illustrate the response process of soil moisture to 24 rainfall for different vegetation types under the humid climate type of the 25 mid-subtropical zone in pure limestone slope lands, thus enriching relevant 26 knowledge systems and providing more scientific bases for the implementation of 27 ecological restoration projects in karst areas. 28

arable land soil layers significantly changed. In addition, in light rain events, only the 22 soil moisture of the grassland and arable land responded. Overall, in this study, 23 quantitative indices were used to illustrate the response process of soil moisture to  is that the properties of bedrock and soil are also important factors that affect the 56 dynamic changes of soil moisture (Zhao and Gao, 2020). Compared with other areas, 57 in karst areas, the bedrock is mostly carbonate rock, and karstification is strong, which 58 makes the soil layer thin in such areas and leads to broken ground surfaces (Deng et   Therefore, the response process of the soil moisture of different vegetation types to 84 rainfall in winter is still an important investigation topic that needs to be accurately 85 studied.

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Based on this, to find out the dynamic response process of the soil moisture of 87 different vegetation types to rainfall events in winter, the response degree, response 88 time, and response rate of the soil moisture of different vegetation types to rainfall in 89 different soil layers were calculated, and the dynamic response process of soil 90 moisture to rainfall was analyzed. Thus, the soil hydrological processes related to   Table 1, and Fig. 1 shows an overview 122 of the sample plots and the distribution of their monitoring points.

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The calculation method of the soil bulk density BD (g/cm 3 ) is as follows: (1) 173 In the formula, 100 is the undisturbed soil volume (cm 3 ).

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The calculation method of the porosity TP (%) is as follows: (2) 176 In the formula, the first 100 is the undisturbed soil volume (cm 3 ), and the second 100 177 is the percentage conversion coefficient.

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The calculation method of the saturated hydraulic conductivity SH (cm/h) is as 179 follows: The organic matter content was determined using the potassium dichromate  composition was measured using a laser particle size analyzer, and the international 202 system was used for particle size classification. The clay particle was <0.002 mm, the 203 powder particle was 0.002～0.02 mm, and the sand particle was 0.02～2 mm.

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According to the international system, The map of the corresponding soil triangle 205 quality determines the type of soil texture. When conducting the soil mechanical 206 composition experiment, apretreatment was performed after removing the calcium 207 carbonate and organic matter, and a dispersant was added and then left to stand for 24 208 hours before using the machine.

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The soil bulk density, soil porosity, saturated hydraulic conductivity, soil particle The ASWI of each soil depth layer at each monitoring point was calculated. To study 273 the relationship between the increase in the soil moisture in the upper and lower layers, 274 we calculated the ratio of the increase in the soil moisture of the two adjacent layers in 275 the same rainfall event:  in the second layer and then decreased with the increase in depth. Also, the ASWI of 319 the shrub and forestland decreased with the increase in depth. In addition, the RSWI 320 was below 100%, indicating that the soil moisture response to rainfall events 321 1 1 / 1 1 / 1 9 1 1 / 2 1 / 1 9 1 2 / 0 2 / 1 9 1 2 / 1 2 / 1 9 1 2 / 2 3 / 1 9 0 1 / 0 2 / 2 0  As shown in Fig. 5a, under a light rain event, the difference in the soil moisture 372 G5 A5 S5 F5 G10 A10 S10 F10 G15 A15 S15 F15 G20 A20 S20 0  The above analysis shows that in the case of light rain, the grassland soil     The results showed that for grassland soil moisture, the response degree, response 523 duration, and response speed to rainfall are largest, longest, and fastest, respectively. with regard to the rainfall response process and enrich the related knowledge system.

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However, whether the response process of soil water to rainfall in winter under other 531 conditions, such as different bedrocks, climate types, vegetation types, and karst areas, 532 will have new characteristics is a further question that needs more investigation.

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The authors declare that they have no known competing financial interests or 535 personal relationships that could have appeared to influence the work reported in this